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356                    HEAVY OILS  (LUBRICATING OILS)

With a pale oil, 10 grams are dissolved in about 150 c.c. of a perfectly
neutral mixture of ether (4 parts) and alcohol (i part) and the solution
titrated with decinormal alcoholic sodium hydroxide in presence of phenolph-
thalein. If the colour of the oil is too intense to admit of observation of
the colour change of phenolphthalein, 10 grams of it are shaken with 100
c.c. of absolute alcohol and 50 c.c. of the separated alcoholic layer titrated
with decinormal alcoholic caustic soda in presence of phenolphthalein.1

The acidity is expressed as sulphuric anhydride or oleic acid, or as the
number of milligrams of potassium hydroxide necessary to neutralise i
gram of the oil, the last being termed the acidity number of the oil; i%
S03 = 7-05% oleic acid = acidity number of 14.

3.  Alkalinity.—This is detected by adding phenolphthalein to another
aliquot part of the water with which the oil was shaken in the determina-
tion of the mineral acids ;  with free alkali a red coloration is obtained.

It must be borne in mind that, if the oil in question contains alkali soaps,
the alkalinity found may be due to partial decomposition (hydrolysis) of the
soap by water.

4.  Determination of the Solid Paraffin and Asphalt.—As in crude
petroleum (q.v., Chemical Tests, 4 and 5).

5.  Detection   of   Oils,   Fats    and   Waxes.—(i)   QUALITATIVE.    5
c.c. of the mineral oil are heated for about 15 minutes in a test-tube with
a stick of caustic soda weighing about 4 grams, either over a naked flame
or, better, in a paraffin bath at 200-210°.    If fatty substances are present,
even only to the extent of 1-2%, the whole mass becomes solid and gelatinous
on cooling.

(2) QUANTITATIVE. If the qualitative test gives a positive result, the
quantitative estimation may be carried out as follows :

(a) By the saponification number determined as indicated for fatty
substances ; about 5 grams of substance are used and, besides alcoholic
potash, an equal quantity of benzene is added, the heating in a reflux appara-
tus being continued for about an hour. The saponification number thus
obtained is divided by 1-85, the result being the percentage of fatty sub-
stances calculated from the mean value of their saponification number.

In presence of wool fat or waxes—which are usually detectable by the odour
and consistency—the results obtained are inaccurate, since these substances
have saponification numbers different from those of fatty substances.

(6) By direct weighing, according to the directions given by Armani
and Roda.no2:

5 grams of the oil are saponified in a flask with alcoholic potash
solution (12 grams of caustic potash in 100 of alcohol), the flask being
immersed in a bath of boiling water. As reflux apparatus, a simple funnel
is placed in the mouth of the flask, so that a large part of the alcohol is

1  According to H. Loebell (Chem. Zeit., 1911, 35, p. 276), the acidity is determined
in 10 c.c. of the oil, using an alcohol-benzene mixture (i : 2) as solvent, alkali blue as
indicator and decinormal alcoholic caustic soda as standard solution.

2  Industria saponiera, Milan, 1912, p. 169;   Ann. Lab. chim. oentrale Gabelle, Vol.
VII, p. 278.water.l2, 22-5.